EZ Cool ,
Theres pros and cons both ways . If you do a one piece the problem is getting it back in there . (1st option) To get it in there you pretty much need to take the rear tail light panel out . once you get into it you'll see in the back the trunk pan is kind of sandwiched between the tail light panel and the trunk pan drop downs and theres just no way to get it up in there without removing the rear panel .
( 2nd option ) Now I can't say for sure this will work because I,m right in the middle of doing mine , but the lower part of my right side wheel well needed repair and so did my right side trunk pan drop down panel . So i removed the drop down and cut about an 1 1/2 of the wheel well ( the rusty part ) off and made a new piece to weld in AFTER I put the trunk pan back in . ( theres photos in my restoration thread ) I,m going to try and slide mine in from the side .
I,ll be putting mine up in there either friday or saturday , I,ll post how it went .
The 7 piece will be way easier to put in but your going have to do a lot of measuring to make sure it will bolt back onto the frame holes .
All this will also depend on who you get the trunk pan from also . I used the one piece from Tamraz and so far ( knock on wood ) it measures up great .
I know Rollaround used the 7 piece from Tamraz . maybe he has some tips .
I know theres a few other guys on here that have done them also .